Summary Understanding the development and expression profile of adult cochlear cell types provides an opportunity to improve the targeting of genetic and therapeutic interventions designed to restore hearing to our patients. In the last year, we have finished our validation of a resource for adult cochlear supporting cell transcriptomes. We demonstrated that adult cochlear supporting cells are transcriptionally distinct from their perinatal counterparts. We established cell type-specific adult cochlear supporting cell transcriptome profiles, and we validated these expression profiles through a combination of both fluorescent immunohistochemistry and in situ hybridization co-localization and qPCR of adult cochlear supporting cells. Furthermore, we demonstrated the relevance of these profiles to the adult human cochlea through immunofluorescent human temporal bone histopathology. Finally, we demonstrated cell cycle regulator expression in adult supporting cells and performed pathway analyses to identify potential mechanisms for facilitating mitotic regeneration (cell proliferation, differentiation, and eventually regeneration) in the adult mammalian cochlea. Our findings demonstrate the importance of characterizing mature as opposed to perinatal supporting cells. Our manuscript has been submitted and while it is under review, the manuscript is also available as a preprint on bioRxiv (https://www.biorxiv.org/content/10.1101/742270v1?rss=1). The raw data has been deposited to GEO and will be made available upon publication. We are also in the process of depositing the data on the gene Expression Analysis Resource (gEAR), a website for visualization and comparative analysis of multi-omic data, with an emphasis on hearing research (https://umgear.org). A significant goal of the Auditory Development and Restoration Program is the characterization of cells within the stria vascularis. The stria vascularis (SV) is housed in the lateral wall of the cochlea and consists of 3 layers composed predominantly of marginal, intermediate, and basal cells, respectively. The SV plays a significant role in inner ear ion homeostasis and generates the endocochlear potential (EP) which is necessary for proper hair cell mechanotransduction and hearing. While channels belonging to SV cell types are known to play crucial roles in EP generation, relatively little is known about gene regulatory networks that underlie the ability of the SV to generate and maintain the EP. In the last year, utilizing single cell and single nucleus transcriptional profiling, we have characterized cellular diversity in the SV during EP development and maintenance and have characterized transcriptome profiles of both known and rare cell populations in the SV. Furthermore, we establish a basis for understanding molecular mechanisms underlying SV function by identifying potential gene regulatory networks as well as druggable gene targets. Finally, we associate known deafness genes with adult SV cell types. This work establishes a basis for dissecting the genetic mechanisms underlying the role of the SV in hearing and will serve as a basis for designing therapeutic approaches to hearing loss related to SV dysfunction. Manuscript is in preparation. Finally, in the last year, we have developed two SV cell type-specific fluorescent reporter BAC transgenic mice. Expression of the transgenes appears to be in the expected cell types and we are in the process of fully characterizing these lines. We intend to publish these lines and make them available to the wider community for use.